Giant planet far away from sun-like stars puzzles astronomers

A team of astronomers led by Dutch scientists immediately took a picture of a gigantic planet orbiting a great distance around a sun-like star. Why this planet is so huge and how it got there is a mystery. The researchers publish their findings in the journal Astronomy and Astrophysics

The planet in question is YSES 2b, 360 light-years from Earth toward the southern constellation of Musca (Latin for The Fly). The gaseous planet is six times heavier than Jupiter, the largest planet in our solar system. The newly discovered planet orbits 110 times as far from its star as Earth is from the sun (or 20 times the distance between the sun and Jupiter). The companion star is only 14 million years old and resembles our childhood sun.

The planet’s great distance from the star is a mystery to astronomers because it doesn’t seem to fit into one of the two best-known models for the formation of large gaseous planets. If the planet had grown far from the star at its present location by means of nuclear accretion, it would be too massive because there is not enough material to make a huge planet at this great distance from the star. If the planet was created by the so-called gravitational instability in the planetary disc, it turns out to be not heavy enough. A third possibility is that the planet formed close to the star through nuclear accretion and then migrated outward. However, such a migration would require the gravitational influence of a second planet, which the researchers have not yet found.

The astronomers will continue to investigate the surroundings of this unusual planet and its star for the foreseeable future and hope to learn more about the system, and will continue to search for other gaseous planets around young, sun-like stars. Today’s telescopes are not yet large enough to make direct images of Earth-like planets around sun-like stars.

Principal researcher Alexander Bohn (Leiden University): “By investigating more Jupiter-like exoplanets in the near future, we will learn more about the formation processes of gas giants around sun-like stars.”

The planet YSES 2b was discovered with the Young suns Exoplanet Survey (YSES). This research already produced the first direct image of a multi-plant system around a sun-like star in 2020. The researchers made their observations in 2018 and 2020 using the Very Large Telescope at the European Southern Observatory (ESO) in Chile. They used the telescope’s SPHERE instrument for this. This instrument was co-developed by the Netherlands and can capture direct and indirect light from exoplanets.